Method of making a joint



March 5, 1963 A. E. FENTIMAN 3,079,681

METHOD OF MAKING A JOINT Original Filed Jan. 18, 1956 2 Sheets-Sheet 1 11 a 12 11 1 lb 14 o 2O 2 30 a 19 21 19 22 f B I T FIG. 2

Iny'entor ARTHUR E PENTIMAN Attorney March 5, 1963 A E. FENTIMAN METHOD OF MAKING A JOINT Original Filed Jan. 18, 1956 2 Sheets-Sheet 2 FIG 3 Inventor ARTHUR E. l-BNTIMAN 4 Attorney United States Patent 3,079,681 METHOD OF MAKING A JOINT Arthur E. Fentiman, Ottawa, Ontario, Canada, assignor to F. Fentiman & Sons, Ltd., Ottawa, Ontario, Canada Original application Jan. 18, 1956, Ser. No. 560,027, now Patent No. 2,895,753, dated July 21, 1959. Divided and this application May 18, 1959, Ser. No. 814,040 Claims. (Cl. 29-525) This invention relates to the method of making a joint designed for use in the fabrication of many units entering into various forms of structures and is a division of my copending application Serial Number 560,027, new Patent No. 2,895,753, Joint, which was a continuation-in-part of applications #450,717, now Patent No. 2,931,467, Structural Framework, and #487,514, now Patent No. 2,964,147, Truss and Components Therefor.

In the past decade great progress has been made in the development and use of new materials such as plastics, alloys and the like and many articles are now made from these new materials, and successfully used in building and other allied arts.

In developing my invention it was necessary to consider its application not only to metal structures but also to other materials which may enter into the fabrication of units suitable for use in the building art, and it will be clear that my invention is not to be restricted to metal joints but applies to a larger field in which joints of other materials find use.

In developing the present invention the building art has been carefully studied and while metal threaded joints and clamps and nuts and bolts have been and are being used with a certain amount of success, in scaffolding and other similar structures, they are subject to many objections.

Ferrous metals enter very largely into the building art, as for instance, in the fabrication of roof principals, and conventional threaded units such as couplings, knees or bends, T-pieces etc., are commonly used in construction work, but the making and assembling of such units is time consuming and necessitates the use of skilled labour which adds to construction costs.

In a threaded joint, part of the inner and/or the outer periphery of the co-acting members is removed in cutting the thread. with the result that the efiective area of the metal at the joint is materiall reduced. It therefore a threaded tubular joint is to be made of a specified strength it usually requires that the tubular body part must be oversize so that the relatively smaller threaded portion of the tube will have the required cross sectional area to provide the desired strength. When solid rods are used the ends could be upset and threaded so that the body of the rods would not require to be increased, but this too is a costly operation.

As the cross sectional area of tubular units located between the threaded ends increases with the square of the diameter of the unit, it will be clear that the weight of the structure will increase very rapidly. Such an increase in weight usually requires that the supporting units for such a structure will have to be proportionately strong and heavily constructed to carry the load.

This question of weight of a structure proportionate to size may be of great importance if the structure is of a knockdown form and has to be shipped by air to outlying places for erection.

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Structures formed of ferrous metal have been successfully used in building structures but unfortunately ferrous metal rusts and deteriorates when exposed to the atmosphere, and if the air is contaminated with acid fumes, as it frequently is in industrial areas, then the deterioration is hastened.

The cutting of threads in the outer periphery of a ferrous tube makes a place of discontinuity of the peripheral metal of the tube, and the sharp indentations of the cut thread constitutes a place of weakness, particularly when the tube is submitted to a movement of contra-fiexure.

Moreover, when building frames are formed of threaded tubular parts, it is difiicult to remove a defective or trace tured threaded tube and replace it with a sound tube without submitting the frame to stresses and strains seldom contemplated when designing or fabricating the frames.

These were a few of the disadvantages with which I was confronted when making my invention, and the conclusion reached was that threaded joints, as we know them, are not always successful when used in the fabrication of building frames or structures.

In seeking a solution of a form of joint it was realized that the joint must not only form the connecting means of the members of a single firm frame, but that provision must be made for connecting thereto other firm frames so that polygonal frames of various forms may be built up possessing great strength and when desired lightness of weight.

The joint may consequently be constructed of any desired metal suitable for the purpose for which it is intended, but the joint may also be constructed of synthetic materials or other non-metallic materials when such may be advantageously employed.

In the selection of materials for making a joint this would be governed by the purpose for which the joint is to be used, and if lightness and strength were required then some of the alloys of the lighter metals may be used to advantage.

In bringing my invention to a successful conclusion and reduction to practice certain objects had to be fulfilled.

One of the objects of my invention is to construct a joint which is easily assembled and easy to take apart, and permits of the removal of a defective unit and the insertion of a replacement part without subjecting the structure of which the joint forms an essential part, to undue stress or strain.

A further object is to construct a joint of a central hub and cooperating radial members, so that the resistance to shear of the members'of the joint will effectively withstand tensile stress applied to the radial members, which stress might otherwise tend to impair the joint.

Another object is to provide a radial member of the joint with an end that is at least partially flat and which may be laterally inserted and driven into a longitudinally extending keyway in a hub.

Still a further object is to form the partially flattened end of a radial member of a joint so that the resiliency of the material forming the member will press the fiattened portion into initmate contact with the walls of a keyway in a hub.

Sill another object is to provide a keyway of a hub and a partially flattened end of a radial member of a joint with co-acting projections in which the resistance of the material of the joint to shear is distributed over V FIGURE 4: is an enlarged the engaging projections in thebest manner to resist any tensile stress applied to the radial member.

A further object is to press the end of a radial member of a joint into a flattened shape with the flattened walls slightly spaced apart and retaining the resiliency of the material in the flattened end.

A further object is to press the end of a radial member of a joint into a partially flattened shape and to form projections thereon by flowing the material of the memher into the projections without cutting or fracturing the outer peripheral wall of the member and so retaining a maximum tensile strength in the radial member.

Another object is to develop a joint which will retain to :a maximum the tensile strength of the materials used in the parts constituting the joint so that the completed 7 jointwill have the highest possible etficiency.

ie'sistanceto shearing over the members of the joint in a'jman'ner progressively increasing in force from the periphery of the hub'to .the root of the keyway. 7

So that'the'nature of, my invention may be more clearly understood, I haveillustrated and described in detail one embodiment of the same, but it must be understood that I donot restrict my invention to' this specific form or method now described but reserve the right to make modifications within the scope of my appended claims.

' In the drawings: 1

"FIGURE 1 is an'end elevation of a hub and a plurality of radial members connected therewith.

FIGURE 2 is an enlarged detailed end elevation of the joint when assembled. e )FIGURE 3' is a similarly enlarged sectional detail of thejointshowing'the" disposition of the recesses and ribs of one of the lateral walls of a'keyway andthe arrangement ofgthe ribs and'recesses of one of the walls of the radial member, the two members being slightly spaced apart ;to' show thecomplemental arrangement'of the ribs and recesses of one member relatively'tothe recesses and ribs of .the other member. v r

I v I end elevation of the'flattened end of a radial member showing the'convex shape of-the'said end with its slightly spaced arcuate walls before engagement with a keyway in the hub.

FIGURE S is an enlargedsection of the flattened end of-a radial member showing the slight arcuate or convex shape of the walls of the flattened end as compressed in a keyway of the hub, as taken on the line 55 of FIGURE land looking in the direction of the arrows.

'-FIGURE 6 is' a vertical longitudinal section of the end o fa'radialmember showing the narrow, heightened space between the partially flattened walls of the member, as taken on'theline of FIGURE 1 and looking the direction of the arrows.

- Like characters'of reference refer tolike parts'in the several-figures i I Y Reterring to the drawingsyAfrepresents a joint comprising a'hub B and a radial member such as the tube C' which may be made ofan extruded metal. The hub Bis formed with a plurality of radially disposed keyways which extend longitudinally throughfthe .length of the hub (i .e.) from end to end., The-number of keyways will depend on the use "to'which .the joint is to be put and in the embodiment illustrated sixkeyways are arranged'eqtiidistziiitlyLspaced around the hub. A

'The laterar'wans's of'the keyway 10 taper towards the bottom of the keyway, and these walls 7 are, formed with a plurality of spaced longitudinally extending recesses 11 the side walls 12 of which are angularly disposed and diverge towards the central longitudinal axial 7 plane of the keyway. The inner wall 13 of these recesses 11 is flat, forming a plane surface of rectangular shape.

Ribs 14 located between the recesses 11 are formed by the angularly disposed side walls 12 and the crests 16 of these ribs adjacent the centre plane of the keyway are flat and form plane surfaces of rectangular shape.

At the bottom of th'e'keyway the angularly disposed walls of the recesses 11 converge as shown at 17.

By reference to FIGURE 2 of the drawings, it will be seen that the angular edge 8 of the crests 16 of the ribs 14 lie in the plane of the taper of the lateral walls 9 of the keyway 10,-and that the angular edges 7 of these 7 mately 4 deg. 45 min. behind the plane-of the normal lateral walls of the keyway. The inner walls 13 ofvthe recesses 11 are disposed at a similar angle asthe crests oftheribs. r

The size anddepth of the recesses 11 progressively increase from adjacent the periphery of the hub B to the bottom of the keyway 10, and the'size'and-height of the. ribs '14 likewise progressively increase from adjacent the peripheral end of the keyway ltltothebottom of the keyway. r

This increase in the size and depth of the recesses and the size and height of theribs cause the keyways 10 to assume a dovetail form in profile; below the-throat 15 of the keyway. V I

This form of keyway is not to be confused with an ordinary dovetail, in that it differs therefrom by providing a' greater contacting area and provides a better angular engagement of the contacting parts of the joint.

The bottom of the keyway 10 simulates 'anenlarged irregular hexagon D, the side walls of which are shorter thanlthe other walls. V r

'lhe radial member C is illustrated as a tube, and-a short length of the end of the. tume is flattened by dies approximately five one thousandths of an inch between the flattened walls, and this permits the walls to be-pressed into closer contact but the walls recover from any de' formation by the resiliency of the metal formingthe walls tending to return the walls totheir sp-aced relationship under circumstances which I shall describe later. g

'Ihe'walls 18 are slightly arcuate or convex in cross section and the solid edges of the flattened walls are slightly tapered and this facilitates entering the edge of the flattened .end of the tube C into the end of a keyway 10 when assembling a joint. g 1. f Theflattening of the walls 18 ,of the end of the tube C is very important as the ribs 19 are'formed'by the displacement of the metal which flows from the recesses 20 to the crests of the ribs 19 which are flat at the crests and the recesses are correspondingly formed so, that they need not be'too deep to give this required shape to the ribs. The pressing of the end of the tube -C (which is drawn tubing), is across 'the grain of the metal of the tube and as the metalof the periphery of the tube is not cut but merely displaced the grain isnot impaired but only slightly displaced andelongated so that the tensile strength of the tube is maintained. As will be observed the displacement of metal from the recesses to the crests of the ribs gives anoverall thickness to the crests whichis considerably greater than the thickness of the tube walls, After this cold working of the'tube end'during theflattening process, the tube is heat treated-and aged, and.

tests have shown that the strength of the tube has not; been impaired but has been maintained.

The ribs 19 and the recesses 20 progressively increase in size towards the bottom end of the flattened walls 18 so that in profile this flattened end resembles a dovetail. The lateral walls 21 of each rib 19 are angularly disposed to the face of the flattened portion 18 of the tube C and these walls converge outwardly to the crests 22 which is substantially rectangular in shape. The recesses 20 between the ribs 19 are bounded by the angularly disposed lateral walls 21 which diverge, and the inner or bottom wall 23 of each recess is substantially of rectangular shape.

The crest 22 of the ribs 19 and the bottom wall 23 of the recesses 20 are angularly disposed at an angle similar to the bottom walls 13 of the recesses 11 and the crests 16 of the ribs 14, so that the ribs and recesses on the end of the tube C are complement-a1 to the recesses 11 and ribs 14 in the side walls 9 of the keyway 10. The flattened walls 18 of the tube C terminates in an enlarged end B similar in shape to the enlarged inner end D of the keyway 10, Le. this enlarged end E simulates an irregular hexagon.

The tapered edge of the flattened end of the tube C is inserted edgewise into the end of the keyway 10, as shown schematically in FlGURE 4, and then the flattened end is driven into engagement with the keyway throughout the entire width of the flattened end. Since the Walls 18 of the flattened end of the tube C are slightly convex and are also slightly spaced apart these walls are pressed towards each other when the joint is assembled, and the resiliency of the metal holds the walls 18 and the ribs 19 and recesses 24 in intimate contact with the walls 9 and the recesses 11 and ribs 14 of the keyway but this pres- 3 sure on the walls 18 does not make any permanent distortion on the flattened end of the tube C since the walls return to, or assume their convex shape when the flattened end of the tube C is disengaged from the keyway 10.

It will be clear that the engagement of the walls, the ribs and recesses are a combination of resilient and frictional contact and that the co-acting recesses and ribs engage each other along their angularly disposed lateral walls so that these contacts are over inclined planes.

When an axial pull is exerted on the tube C separation of the joint A is resisted by the inclined planes formed by the angular disposition of the aforesaid lateral Walls of the ribs and recesses which play a very important part in this matter. In this wise the force will be over these inclined planes and may be resolved into two components, viz., a force normally at right angles to the walls of the keyway which force is resisted by the walls of the keyway, and a second shearing force which is outward or radial in direction.

The longitudinal pull on the tube C is overcome by the resistance to shear of the ribs 11 on the walls 9 of the keyway 10, and the ribs 19 on the walls 18 on the flattened end of the tube C.

This resistance will be greatest at the root of the keyway 10 where the enlarged end E of the flattened end of the tube C engages the inclined wall of the bottomrnost rib 11 and this resistance gradually diminishes towards the peripheral end of the keyway as the gradually diminishing ribs engage each other.

It is to provide a proper distribution of this resistance to shear that the recesses and ribs of the keyway 10 and the recesses and ribs of the flattened walls 1'8 of the tube C increase in size from the periphery of the hub to the bottom of the keyway.

The number of ribs and recesses in the walls 9 of a keyway 10 and the flattened walls 18 of a tube C will depend on the specific use to which the joint may be put, and while for small joints there will be at least two ribs and recesses used on each side wall of a keyway and a similar number of recesses and ribs on the flattened end of a tube C, this number will be increased on larger types of joints when such is found desirable or necessary. The reference to a plurality of recesses and ribs as used 6 throughout the specification must be interpreted in the sense set out above.

In the embodiment of the invention which I have illustrated I have found that by arranging the lateral walls of the recesses and ribs at an angle of approximately 30 and graduating the size of these recesses and ribs, that the resisting force to shear can be advantageously allocated as follows: approximately 15% near the periphery of the hub, about 25% midway of the depth of the keyway and at the root of the keyway.

This distribution was arrived at after considerable study and innumerable tests of the joint, in which the lateral walls of the ribs and recesses were varied from a right angle to an acute angle. This angle of 30 as illustrated in the drawings may be varied very slightly if so desired. It will be noted that all the walls between the recesses and ribs are filleted or rounded at their line of junction, and the tube merges into the flattened end at an acute angle of approximately 26 thus eliminating any sharp angles.

When fashioning my joint and describing it I have referred to the radial member as a metal tube which may be an alloy of one of the lighter metals which have a grain structure suitable for the purpose, and after pressing the ends of the tube C to the desired shape I submit these tubes C to a heat treatment and ageing which give beneficial results before they are assembled into the joint. This type of joint however can be used with ferrous metals but in this case I submit the ends of the tubes to flattening when hot, and the ends may be annealed and aged before assembling the joint. Preferably the materials usedin the making of these joints have an inherent resiliency which is retained even in the flattening of the tubular members to that it is contributory in the making of a strong tight joint. The joint has wide uses and may be constructed of non-metallic materials if and when desired. Additionally, when desired, the radial members may be solid and of other than tubular cross section.

The members of the joint are easily assembled and after the edge of the flat end of the radial tube is inser-ted in the end of the keyway it may be driven into posi ion to complete the joint.

This assembly entails only the use of a hammerQso that skilled labour is not essential for this operation, and the joint may be taken apart with the same case by simply striking the radial or tubular member with a hammer in a line paralleling the axis of the hub to disengage it from the end of the keyway.

Having thus described the invention, what is claimed as new 1s:

1. The method of forming a joint between two elements by flattening the end of one tubular element while simultaneously forming on said end transversely extending ribs and recesses of graduated size increasing toward the end of the element by displacing material from the recesses and flowing it into the ribs, allowing the flattened end some partial elastic recovery from the flattening deformation so as to produce slightly convex walls that are slightly spaced apart, and forcing the end of said element edgeways into a second element having a keyway with lateral diverging walls and corresponding ribs and recesses but of a width less than the thickest part of the partially recovered flattened end of said first element.

2. The method of forming a joint between a tube and a co-acting element by simultaneously flattening the end of the tube and forming on said end transversely .extending ribs and recesses of graduated size increasing toward the end of the element by displacing material from the recesses and flowing it into the ribs, allowing the flattened end some partial elastic recovery from the flattening deformation so as to produce slightly convex walls that are slightly spaced apart, and forcing the partially recovered flattened end of said tube edgeways into a coacting element having a correspondingly ribbed and recessed keyway with laterally diverging walls spaced less than the thickest part of the partially recovered flattened end of said tube whereby theslightly convex spaced walls of said tube end are compressed in the keyway ofn said co-acting element and friotionally held therein.

3. The method of forming a joint between a tube and V a hub by flattening the end of the tube and simultaneously a forming on said end transversely extending ribs and recesses of graduated size increasing toward the end'of the element by displacing material from the recesses and flowing it into the ribs, allowing the flattened end some partial elastic recovery from the flattening deformation so as to produce slightly convex walls that are slightly spaced apart, and forcing the end of said tube edgeways into a co-acting element having a correspondingly ribbed and recessed keyway with laterally diverging walls spaced less than the thickest'part of the partially recovered flattened endrof said tube whereby the slightly convex spaced walls of said tube end are compressed in the keyway of saidco-acting element and frictionally held therein and placed from the recess into the built up material of the rib, said approximately flat end being allowed some partial elastic recovery from the flattening deformation so as to produce slightly convex Walls that areslightly spaced apart, forming a keyway with complementary recesses and ribs in the lateral wallsthereof in thesecond member, with the inner walls of the recesses and the crests of the ribs thereof being flat, graduating the size of the ribs and the recesses progressively and increasingly from the top to the bottom of the key,and forcing the flattened end of the first element edgewise into the keyway of the second element thereby compressing the slightly resilient convex form thereof.

-5. The method of forming a joint between two elements one of which is tubular by simultaneously making the end of the tubular element'app'roximately flat and forming the peripheral material of the flattened element into ribs with recesses therebetween, with the crests of r the ribs and the inner walls of the recesses being formed flat by flowing material displaced from the recesses into the ribs, allowing the flattened end partial elastic recovery from the flattening deformation so as to produce slightly convex walls that are slightly spaced apart, forming a keyway with complementary recesses and ribs in the lateral walls thereof in the second element, with the inner walls of the recesses and thecrests of the ribs being formed flat, the rear edges of the flattened crests of the ribs lying in a plane of the taper of the lateral walls of the keyway with the forward edges of the flattened crests lying behind the said plane, and graduating the size of the ribs and the recesses in the two elements to distribute a resistance to shearing of the elements of the joint progressively and increasingly from the top to the bottom of the keyway, and forcing the flattened end of the first element edgewise into the keyway of the second element thereby compressing theslightly'resilient convex form thereof.

6. The method of forming a joint between two-elements one of which is tubular by making the end of the tubular element approximately flat by deformation and the crests of the ribs and the inner walls of the recesses being formed flat, the plane of the flat crests and the plane of the flat inner walls of the recesses diverging towards the front end of the element, allowing the flatc2 tened end partial elastic recovery from theflattening deformation so as to produce slightly convex walls that are slightly spaced apart, forming a keyway with complementary recesses and ribs in its lateral walls in the second element with the inner walls of the recesses and the crests of the ribs being flat, and graduating the-size of the recesses and ribs in the second element to coact with the ribs and recesses in the first element thereby distributing a resistance to shearing of the elements of the joint progressively from the top to the bottom of the keyway in the approximate ratios of 15% at the entrance to the keyway, 25% at the middle of the keyway, and 60% at the bottom of the keyway and forcing the flattened end or" the first element edgewise into the keyway of the second element thereby compressing the slightly resilient convex form thereof.

7. The method of making a joint as described and claimed in claim 6 wherein the plane of the crests of the ribs and the plane of the inner walls of the recesses "diverge at an angle of approximately 4.45'.

8. The method of making a joint between two elements com-prising forming a keyway in one element having open ends and an open top, with the lateral walls diverging towards the bottom of the keyway and simultaneously forming-ridges with recesses therebetweenin the lateral walls of the keyway, the ridges and recesses gradually increasing in size from the top of the keyway to the bottom thereof, substantially flattening by deformation one end of the other element which is tubular and without rupture simultaneously forming thereon recesses and ridges complementary with the ridge-sand-recesses on the lateral walls of the keyway, the recesses and ridges of the second element extending transversely across the flattened end of the element, allowing the flattened end of said second element some'partial elastic recovery from the flattening deformation so as to produce slightly convex walls that are slightly spaced apart, and pressing the partially recovered flattened end of said second element edgeways into one end of the keyway in said first element so that the recesses and ridges of the second element frictionally engage the recesses and ridges in the keyway of the first element to form thejoint'with a gradient of resistance to separation of the elements" by shearing, such resistance progressively increasing from the top' of the keyway to the bottom thereof.

9. The method of making a disengageable joint betweentwo members comprising forming one member with an open ended longitudina ly extending keyway, substantially flattening by deformation anend' of'the second member which is of tubular form' and simultaneousy forming thereon recesses andridge's complementary with the ridges and recesseson the lateral walls of the keyway, the recesse's'andridgesof the second element extending transversely across the flattened end of the element, allowing said flattened end some partial elastic recovery fr'omthe flattening deformation so that it remains thicker at the center than at the edges,'the thickness of the said edges being less than the width of the keyway in the first member and the thickness of the center part of the end being greater'than the width of the said keyway, introducing the said end of said second member edgewise into the keyway of the first member, and forcing the same longitudina ly into said keyway to compress and flatten thethickened center part thereof thereby causing said end to frictionally engage the confronting walls of the keyway. I

10. The method of making a disengageable joint between two elements comprising formingan elongated extrusion with radially disposed keyways running longitudinally thereof and each having open ends and an open top and lateral walls diverging toward the bottom, simultaneously forming ribs'and recesses in the walTs of said keyways of gradually increasing size toward the bottom of the keyway, substantially'flattening the end of a second element which is of tubular form and simultaneously forming thereon transverse ribs and recesses of graduated size complementary to those in the keyways of said elongated extrusion by flowing material displaced from the recesses into the ries, aliowing said flattened end some measure of elastic recovery from the flattening deformation so that it remains slightly thicker at the center than at the edges, cutting said extrusion into lengths corresponding to the width of the flattened end of said second element, and forcing the substantially flattened and ssmewhat resilient end of said second element edgeways into one of the keyways in one of the lengths of said extrusion.

References {Iited in the file of this patent UNITED STATES PATENTS Burvenick Dec. 15, 1931 Atkinson Oct. 7, 1952 Steinhauer Sept. 11, 1956 Tunstall et a1 Apr. 15, 1958 FOREIGN PATENTS Canada June 17, 1952 

1. THE METHOD OF FORMING A JOINT BETWEEN TWO ELEMENTS BY FLATTENING THE END OF ONE TUBULAR ELEMENT WHILE SIMULTANEOUSLY FORMING ON SAID END TRANSVERSELY EXTENDING RIBS AND RECESSES OF GRADUATED SIZE INCREASING TOWARD THE END OF THE ELEMENT BY DISPLACING MATERIAL FROM THE RECESSES AND FLOWING IT INTO THE RIBS, ALLOWING THE FLATTENED END SOME PARTIAL ELASTIC RECOVERY FROM THE FLATTENING DEFORMATION SO AS TO PRODUCE SLIGHTLY CONVEX WALLS THAT ARE SLIGHTLY SPACED APART, AND FORCING THE END OF SAID ELEMENT EDGEWAYS INTO A SECOND ELEMENT HAVING A KEYWAY WITH LATERAL DIVERGING WALLS AND CORRESPONDING RIBS AND RECESSES BUT OF A WIDTH LESS THAN THE THICKEST PART OF THE PARTIALLY RECOVERED FLATTENED END OF SAID FIRST ELEMENT. 